System and method of coating substrates and assembling devices having coated elements

ABSTRACT

A system and method of coating curved substrates and assembling devices having coated elements. The system and method are of particular utility in the manufacture of lamps having a coating formed on the hermetically sealed light emitting chamber of the lamp. The system and method includes, inter alia, an improved uniform coating process and apparatus, improved throughput in the coating process, a reduction in bad coating losses, improved baking processes, and an improved method and apparatus for aligning the filament of a halogen lamp achieved by performing the step of coating of the light emitting chamber prior to the step of sealing the chamber.

BACKGROUND OF THE INVENTION

The present invention relates to the fields of forming coatings onsubstrates and assembling devices having coated elements.

The deposition of materials to form coatings on curved substrates iswell known and finds utility, for example, in the manufacture of lamps.In the manufacture of lamps, particularly lamps which include ahermetically sealed light emitting chamber (i.e., a lamp burner) such ashalogen lamps or high intensity discharge (“HID”) lamps, it is oftendesirable to deposit one or more materials to form a coating on at leasta portion of the surface of the lamp burner. For example, it is wellknown to deposit materials such as infrared reflecting (“IRR”) material,ultraviolet reflecting material, heat reflecting material, and visiblespectrum radiation reflecting material to form coatings on the surfaceof lamp burners.

A known method of manufacturing lamps having a coating formed on atleast a portion of the surface of the lamp burner includes thesequential steps of (i) providing a lamp burner envelope formed from agenerally tubular section of light transmitting material; (ii)positioning one or more electrical leads so that each lead provides anelectrical connection from the interior of the light emitting chamber tothe exterior of the chamber; (iii) sealing the lamp burner envelope tohermetically seal the burner envelope to the leads to thereby seal thelight emitting chamber; and then (iv) depositing one or more materialsto form a coating on at least a portion of the surface of the lampburner.

There are many disadvantages in this method of manufacturing such lampsdue to the sequence of the steps of (a) sealing the lamp burner and (b)forming the coating on the sealed lamp burner. Some of the disadvantagesresult from the difficulty of uniformly depositing the material ormaterials on the elongated shape and generally circular cross-section ofthe lamp burners, a process which requires the rotation of eachindividual lamp burner about its longitudinal axis from the outside oncethe leads are installed and the ends of the burner are sealed. Otherdisadvantages include the limited throughput in the deposition processas a result of the amount of area occupied by the carrier required tohold and rotate each lamp burner. Still other disadvantages result fromthe limitation on the temperature of the reactive process caused by thepresence of the elements of the burner other than the envelope. Furtherdisadvantages result from the inability to test the quality of thecoating before the coated substrate is used in additional manufacturingsteps, e.g., the time and expense of completing the burner beforediscovering a defective coating results in the loss of the entire burnerrather than the relatively inexpensive, defectively coated burnerenvelope. Still other disadvantages result from the inability to use thecoating to facilitate other manufacturing steps such as the positioningof the leads within the envelope in the aligning and sealing process.

With respect to the difficulty in obtaining uniform deposition, theprocesses used to form coatings on substrates such as lamp burnersinclude chemical vapor deposition (“CVD”) and sputter deposition. Oneprior art method and apparatus for forming a coating on substrates bysputter deposition is disclosed in U.S. Pat. No. 5,849,162 to Bartolomeiet al., the content of which is incorporated herein by reference. In theBartolomei et al. process, one or more substrates are supported by acarrier and carried past one or more sources of the material ormaterials to be deposited, e.g., sputtering targets in a sputterdeposition process, by a rotating drum or a linearly transported planarsurface.

It is desirable that the materials deposited on the surface of the lampburner form a coating which possesses uniform physical characteristicsthroughout the coated surface about the circumference of the lampburner. In this way the physical characteristics of the coating on anyone portion of the surface of the lamp burner are the same as thephysical characteristics of the coating on the other portions of thesurface of the lamp burner.

A known process for uniformly coating elongated objects having agenerally circular cross-section, here described in connection with thecoating of lamp burners, includes the steps of (a) supporting an arrayof the lamp burners on a carrier (such as a cylindrical drum or planarsurface as disclosed in Bartolomei et al.); (b) rotating each lampburner in the array about its longitudinal axis; and (c) carrying therotating array past one or more sources of the material or materials tobe deposited. By rotating each lamp burner about its longitudinal axiswhile depositing the material or materials on the selected portions ofthe surface of the lamp burner to form the coating, each portion of thecircumference of the lamp burner the material or materials deposited maybe uniformly deposited about the circumference of each lamp burner thusproviding uniformity in the physical characteristics of the coatingabout the entire coated surface of the lamp burner.

The mounting of each end of each lamp burner in the array to amechanical means for rotating the burner requires redundant, complex andexpensive tooling in the coating apparatus. In one aspect, it is anobject of the present invention to provide a novel coating method andapparatus for forming a uniform coating on an array of lamp burnerenvelopes which requires less complex and thus less expensive toolingfor the rotation of each lamp burner or other substrate about itslongitudinal axis during the coating process. This and other objects maybe achieved by the novel apparatus and method for rotating a pluralityof lamp burner envelopes about the longitudinal axis thereof whilemoving the envelopes past one or more sputtering sources.

With regard to the throughput of the deposition process, it is desirableto maximize the throughput by maximizing the number of substrates whichmay be mounted on the carrier. It is common in known processes for eachindividual substrate rotation means to require more space on the carrierthan the individual substrate. Because each substrate is mounted on anindividual axial rotation means, the maximum density of the array oflamp burners which may be carried per surface area of the carrier isseverely limited. In another aspect, it is an object of the presentinvention to provide a novel method and apparatus for forming a coatingon an array of substrates with significantly improved throughput.

With respect to temperature limitations, it is often desirable to coatsubstrates using a reactive coating method such as disclosed in theaforementioned Bartolomei et al. patent. In that process, a materialsuch as silicon is deposited and reacted with a gas such as oxygen sothat the coating on the surface of the substrate comprises silicondioxide, a reaction which generally occurs more readily at highertemperatures. While the temperature at which the reactive coating isdeposited on the substrate in a reactive sputter deposition process isgenerally within the range of 25° C. to 125° C. and is limited to about200° C. or below, the time required to form a completely reacted coatingon a substrate may be reduced by depositing the coating material ormaterials at a rate in excess of the rate at which all of the depositedmaterials will be reacted with the reactive gas in the reactive coatingapparatus, and thereafter removing the substrates from the reactivecoating apparatus for baking in a reactive atmosphere at temperaturesgreater than the temperature of the deposition process. The elevation oftemperature in the baking process reduces the total time required toobtain a fully reacted coating on a substrate and thus improves theefficacy of the coating process. Generally, the amount of time requiredto complete the reaction is inversely related to the baking temperature,and the uniformity of the coating is generally enhanced by higher bakingtemperatures.

However, the temperature of the baking process may be significantlylimited by the non-substrate components being baked. Where, for example,electrical leads and other components of a completed lamp burner arepresent, such electrical leads will be damaged if exposed to hightemperatures in a reactive atmosphere such as air which contains asignificant amount of oxygen. For example, the baking temperature of alamp burner having tungsten and molybdenum electrical leads must belimited to less than about 400° C. in an atmosphere comprisingessentially of normal dry air to prevent damage to the electrical leadsdue to oxidation of the leads. Thus, the baking temperature of the lampburners must be limited to prevent damage to the leads, and this limitsthe advantage of the baking process.

In another aspect, it is an object of the present invention to provide anovel method and apparatus for manufacturing lamps which avoids thebaking temperature limitation imposed by the inclusion of non-substratecomponents in the device coated. In other aspects, it is an object ofthe present invention to provide to provide a novel method of bakingcoated lamp burner envelopes.

With respect to the losses associated with the defective coating ofcompleted products, there will be “bad coating losses” in any coatingprocess in which the coating is of unacceptable quality. Yet anotherdisadvantage of performing additional manufacturing steps before thesubstrate is coated results in the loss of the entire lamp burner,including the components used as well as the time and expense incurredin performing the additional manufacturing steps. In lamp burners, forexample, the electrical leads and the time positioning the leads andsealing the lamp burner envelopes represents a significant expense.Where the quality of the coating can be tested before any additionalmanufacturing steps are performed, the loss from a defective coating islimited to the substrate. In another aspect, it is an object of thepresent invention to provide a novel method and apparatus formanufacturing coated substrates in which the cost of bad coating lossesis significantly reduced.

In the manufacture of certain products such as halogen lamps having afilament, it is known that an IRR coating on at least a portion of thesurface of the halogen lamp burner improve the operating efficiency ofthe lamp, i.e., the IRR coating reflects the infrared radiation emittedin the light emitting chamber back toward the filament to raise thetemperature of the filament and thereby reduce the power necessary tooperate the lamp. The position of the filament relative to the lampburner envelope is critical in optimizing the advantage in operatingefficiency of the lamp from the use of an IRR coating on the lampburner. Where the burner is assembled prior to coating, the existence ofthe IRR coating is not available in determining the optimum position ofthe filament. Known methods require the use of time consuming andcomplex apparatus to optically and mechanically position the filamentprior to hermetically sealing the burner envelope to the leads. In yetanother aspect, it is an object of the present invention to provide anovel method and apparatus for determining the optimum position of thefilament of a halogen lamp relative to the lamp burner envelope. Inother aspects, the methods and apparatus of the present invention arelow in cost and easy to perform, facilitated by measuring the electricalresistance of the filament, and facilitated by measuring the powerapplied to the filament to maintain a constant temperature of thefilament.

Where many of the disadvantages of completing the device prior to itscoating are obviated by coating of the substrate prior to the furthermanufacturing steps, it becomes important to protect the coating fromdamage during the further manufacturing steps.

Where the substrate is coated prior to the additional manufacturingsteps, there is the possibility of damage to the coating in the furthermanufacturing steps. For example in the manufacture of lamps where thelamp burner envelope is formed from glass or quartz, the step ofhermetically sealing the burner envelope to the electrical leadsincludes the pinching of portions of the lamp burner envelope which havebeen raised to about 1700° C.-2000° C. Where the lamp burner envelope isformed from ceramic material, the step of hermetically sealing theburner envelope to the electrical leads includes the melting of a fritby raising its temperature to about 1700° C. Such temperatures maydamage the coating. In another aspect, it is an object of the presentinvention to provide a method and apparatus for preventing damage to thecoating formed on a lamp burner envelope during the sealing of theenvelope. In additional aspects, this object may be realized bymechanical shielding and by a novel protective coating to both preventdamage to the IRR coating during the sealing of the lamp burner envelopeand reduce the loss of infrared radiation during the operation of thelamp.

These and many other objects and advantages of the present inventionwill be readily apparent to one skilled in the art to which theinvention pertains from a perusal of the claims, the appended drawings,and the following detailed description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a front pictorial view of a portion of a generally tubularsection from which halogen lamp burner envelopes may be formed.

FIG. 1 b is a front pictorial view of a halogen lamp burner envelope.

FIG. 2 a is a front pictorial view of a portion of a generally tubularsection from which HID lamp burner envelopes may be formed.

FIG. 2 b is a front pictorial view of an HID lamp burner envelope fromwhich a pinched body arc tube may be formed.

FIG. 2 c is a front pictorial view of a portion of a generally tubularsection from which HID lamp burner envelopes may be formed.

FIG. 2 d is a front pictorial view of an HID lamp burner envelope fromwhich a formed body arc tube may be formed.

FIG. 3 is a schematic representation of a prior art halogen lamp burnerin longitudinal cross-section in the plane of the pinch seals.

FIG. 4 is a schematic representation of a prior art pinched body arctube in longitudinal cross-section in the plane of the pinch seals.

FIG. 5 is a schematic representation of a portion of a prior art carrierillustrating individual lamp burners supported thereon.

FIG. 6 is a schematic representation of a portion a carrier of oneembodiment of the coating apparatus of the present inventionillustrating lamp burner envelopes supported thereon.

FIG. 7 is a schematic representation of a cylindrical carrier of oneembodiment of the coating apparatus of the present inventionillustrating a plurality of axial rotation means supported thereon.

FIG. 8 is schematic representation of a portion a carrier of oneembodiment of the coating apparatus of the present inventionillustrating an axial rotation means having a plurality of lamp burnerenvelopes supported thereon.

FIGS. 9 a and 9 b are schematic representations of cylindrical carriersof embodiments of the coating apparatus of the present inventionillustrating a plurality of axial rotation means supported thereonhaving improved lateral spacing.

FIG. 10 a is a schematic representation illustrating a target and maskof one embodiment of the coating apparatus of the present invention.

FIG. 10 b is a section taken through line b-b of FIG. 10 a.

FIG. 11 is a schematic representation illustrating a conventional pinchsealing process for glass or quartz glass lamp burner envelopes.

FIG. 12 is a schematic representation illustrating a conventional fritsealing process for ceramic lamp burner envelopes.

FIG. 13 is a schematic representation illustrating one embodiment of theheat reflective shield of the present invention for the pinch sealingprocess.

FIG. 14 is a schematic representation illustrating one embodiment of theheat reflective coating of the present invention for the pinch sealingprocess.

FIG. 15 is a schematic representation illustrating one embodiment of thepresent invention for determining the position of a filament relative tothe coated burner envelope of a halogen lamp.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to the deposition of materials onsubstrates to form coatings and finds utility in the manufacture oflamps wherein a coating is formed on at least a portion of the surfaceof the lamp burner. The present invention relates generally to themanufacture of lamps but for convenience will be described withreference to the manufacture of halogen lamps and HID lamps.

It is well known to make halogen or HID lamps having a coating formed ona portion of the surface of the lamp burner. Such lamps are typicallymade by the sequential steps of (i) forming the lamp burner envelopefrom a generally tubular section of light transmitting material, (ii)positioning electrical leads and/or electrodes relative to the lampburner envelope, (iii) hermetically sealing the burner envelope to theelectrical leads to thereby seal the light emitting chamber of the lamp,and (iv) forming a coating on a portion of the surface of the lampburner.

FIG. 1 a illustrates a portion of a generally tubular section 10 oflight transmitting material from which the lamp burner envelopes forhalogen lamps may be formed. With reference to FIGS. 1 a and 1 b, thesection 10 may comprise light transmitting material such as glass,quartz glass, or ceramic and may include bulbous portions 12 spacedapart along its length. The section 10 may be cut between the bulbousportions 12 such as at line A-A to form the individual halogen lampburner envelopes such as shown in FIG. 1 b with a bulbous portion 12 andend portions 16.

FIGS. 2 a and 2 c each illustrate a portion of a generally tubularsection 18,19 of light transmitting material such as glass, quartzglass, or ceramics from which the lamp burner envelopes for HID lampshaving a pinched body arc tube and a formed body arc tube respectivelymay be formed. With reference to FIGS. 2 a and 2 c, the section 18 maybe cut transversely to its length at predetermined locations such as atline B-B to form individual HID lamp burner envelopes as illustrated inFIG. 2 b. The section 19 includes bulbous portions 21 spaced apart alongits length and may be cut along the portions of the section 19 betweenthe bulbous portions 21 such as at line B-B to form the individual lampburner envelopes. FIG. 2 d illustrates an individual HID lamp burnerenvelope 23 from which a formed body arc tube including a bulbousportion 21 and end portions 25 may be formed.

In one aspect of the present invention, a novel method of manufacturinglamps lamps having a coating formed on the surface of the lamp burner isprovided wherein the step of forming the coating is performed by formingthe coating on the surface of the sections 10,18,19 before cutting thesections 10,18,19 to form the individual lamp burner envelopes 14,20,23.

FIG. 3 illustrates a lamp burner 22 for a halogen lamp. As illustratedin FIG. 3, the halogen lamp burner 22 comprises a generally tubular lampburner envelope 14 having a bulbous portion 12 and end portions 16. Thelamp burner envelope 14 may be formed from glass or quartz glass andpinch sealed or the lamp burner envelope 14 may be formed from ceramicmaterial and frit sealed.

In the disclosed embodiment, the lamp burner envelope 14 is formed froma material such as glass or quartz glass. A coating 34 is formed on aportion of the exterior surface of the lamp burner envelope 14 and afilament 28 is positioned within the chamber 26. Each end portion 16includes a pinch seal 24 to hermetically seal the light emitting chamber26 from the exterior of the burner envelope 14. A foil 32 may be sealedin each pinch seal 24 to provide an electrical connection between thefilament 28 and the lead wires 30, thereby providing electricalconnections from the interior of the chamber 26 to the exterior of thelamp burner 22.

FIG. 4 illustrates a lamp burner 36 for an HID lamp having a pinchedbody arc tube. As shown in FIG. 4, the HID lamp burner 36 (i.e., arctube) comprises a generally cylindrical lamp burner envelope 20 having acentral portion 38 and flattened end portions 40. The lamp burnerenvelope 20 is formed from a material such as glass or quartz glass anda coating 52 is formed on at least a portion of the exterior surface ofthe burner envelope 20. Each end portion 40 is flattened to form a pinchseal 42 to hermetically seal a light emitting chamber 44 from theexterior of the lamp burner envelope 20. The electrodes 46 arepositioned at each end of the chamber 44 and a foil 48 is sealed in eachpinch seal 42 to provide an electrical connection between one of theelectrodes 46 and a lead wire 50, thereby providing an electricalconnection from the interior of the chamber 44 to the exterior of thelamp burner 36.

It is an important aspect of the present invention that the coating beformed on the lamp burner envelope 14,20 before the steps of completionof the manufacture of the burner by positioning the electrical leads28,30 or 46,50 and by sealing the lamp burner envelope 14,20 to theelectrical leads.

Obtaining Uniform Coatings and Process Throughput:

In the manufacture of lamps, it is desirable that the coating 34,52possess uniform characteristics about the circumference of the burnerenvelope 14,20. This is achieved in known methods by the movement of anarray of lamp burners 22 past one or more sources of the material ormaterials to be deposited, while rotating each lamp burner 22 about itslongitudinal axis.

FIG. 5 shows a portion of a prior art carrier having an array of lampburners supported thereon. The surface of the portion of the carrier 54illustrated in FIG. 5 may be a flat surface which moves the lamp burnerslinearly past the sources of deposition material in an in-line sputterdeposition process, or may be the cylindrical surface of a drum whichmoves the lamp burners past the sources of deposition material as thedrum rotates about its longitudinal axis in a batch sputter depositionprocess.

With reference to FIG. 5, the halogen lamp burners 22 are supported onthe portion of the carrier 54 which carries the lamp burners 22 in thedirection of arrow 56. Each individual lamp burner 22 is supported ateach end 58 by an individual axial rotation means 60 which includessupports 62,64 and a means (not shown) to rotate the lamp. Each axialrotation means 60 rotates the lamp burner 22 supported thereon about thelongitudinal axis of the lamp burner 22 in the direction shown by arrows66. The means to support and to rotate the individual burners requirescomplex and expensive tooling and, as is apparent from FIG. 5, thenumber of lamp burners 22 supported on the carrier 54 is limited by thenumber of supports 60 which may be carried by the carrier 54. Thissignificantly limits the throughput of the coating process.

Where the step of forming the coating is performed before the steps ofpositioning the electrical leads and sealing the lamp burner envelopes,the density of the burners on the carrier and the throughput of thesystem are significantly enhanced. For example, FIG. 6 shows a portionof a carrier moving an array of lamp burner envelopes 14 in thedirection of the arrow 72 past one or more sources of depositionmaterial (not shown). As illustrated, several lamp burner envelopes 14are supported on a single axial rotation means 74 which may include thesupports 76,78 and a rod 80 attached thereto. Any suitable conventionalmeans (not shown) may be used to rotate the rod 80 about itslongitudinal axis in the direction of the arrow 82. Because the ends ofthe lamp burner envelopes 14 are not sealed, the lamp burner envelopes14 may be internally supported on the rod 80 such that rotation of therod 80 will rotate all of the lamp burner envelopes 14 supportedthereon.

The axial rotation means 74 may be carried by a generally planar carrierin an in-line sputter deposition process or by a generally cylindricalcarrier (i.e. drum) in a batch sputter deposition process. FIG. 7illustrates a preferred embodiment of the drum in a batch sputterdeposition apparatus wherein the rotational axis of the drum is verticaland the drum 90 rotates about its vertical longitudinal axis 91 in thedirection shown by arrow 93. One or more axial rotation means 74 may becarried by the drum 90 spaced around the circumference thereof with therods 80 vertical.

As shown in the portion of the surface of a drum shown in FIG. 8, theaxial rotation means 74 includes the rod 80 which is supported at eachend on the portion of the carrier 92 by the supports 76,78. The rod 80is an elongated generally rigid member which may have any shapecross-section but must have a cross-sectional dimension small enough sothat the rod 80 will pass through the generally tubular lamp burnerenvelopes 14 supported thereon.

The lamp burner envelopes 14, integrally connected as shown in FIG. 1 a,or separated as shown in FIG. 1 b, may be mounted on the rotation means74 by detaching the rod 80 from either support 76,78 and sliding thegenerally tubular burner envelopes 14 over the rod 80 so that the axisformed by the rod 80 is coincident with the longitudinal axis of thelamp burner envelopes 14 supported thereon.

In one embodiment, the lamp burner envelopes 94,96 may be supported onthe rod 80 so that rotation of the rod 80 will rotate the lamp burnerenvelopes 94,96 supported thereon, i.e., there is no relative rotationalmotion between the rod and the lamp burner envelopes supported thereon.

In the embodiment of the present invention wherein the rod 80 isvertical, the lowest lamp burner envelope 94 supported by the rod 80 maybe secured to the rod 80 by any suitable conventional means to preventrelative rotational motion between the rod 80 and the lamp burnerenvelope, and each of the remaining lamp burner envelopes 96 supportedby the rod 80 will rotate with the lowest lamp burner envelope 94 due tofrictional engagement with the underlying lamp burner envelope.

The means to prevent relative rotational motion between the rod 80 andthe lowest lamp burner envelope 94 may be a mechanical clamp 84.Alternatively, the surface of the rod 80 may comprise a resilientmaterial slightly compressed by the internal wall of the burner envelope94 and remain in frictional engagement with the lowest, or all, of theburners.

The friction between the adjacent burner envelopes may be enhanced byplacing a washer 86 of frictional material between the adjacent lampburner envelopes, by causing the edges 88 of the lamp burner envelopesto be roughened, or by placing a resilient sleeve 99 over the adjacentend portions 97 of the lamp burner envelopes 96 to grip the ends ofadjacent burners.

The uniform coating may also be formed on the integral section 10 beforethe section is cut to form the individual burner envelopes, and thecoating may be patterned to leave uncoated space on the section betweenburner envelopes. Alternatively, the sleeve 99 may provide shielding.

As illustrated in FIGS. 6, 7, and 8, a single axial rotation means 74may support and rotate a plurality of lamp burner envelopes 14 thusreducing the number of axial rotation means required to rotate each ofthe lamp burner envelopes in an array of lamp burner envelopes carriedby the carrier. Thus the tooling required in the coating apparatus andthe cost associated therewith is reduced. It also increases the densityof the array in that the space consumed by the rotating means ismaterially reduced, and thus improves the throughput.

Throughput of the coating apparatus may be improved by reducing thelateral spacing between laterally adjacent rods. As shown in FIG. 9, thespacing between the laterally adjacent rotational means 60 illustratedin FIG. 5 may be reduced by offsetting the axial position of thelaterally adjacent axial rotation means 60.

It is often desirable to prevent the deposition of the coating materialson selected portions of the surface to be coated. This may be achievedby masking the selected portions, i.e. providing a physical barrier toprevent the deposition of the coating material on the selected portions.The position of the physical barrier may be fixed relative to theposition of the sources of the material to be deposited, or may becarried by the carrier in a position fixed relative to the position ofthe substrates.

As shown in FIG. 10, a section of the surface 100 of a sputtering targetmay be masked by a mask 102 fixed relative thereto by mounting on thetarget supporting structure. Alternatively, the mask may be carried bythe carrier in a fixed position relative to the substrates being coated.In either event, the mask may be any mechanical barrier which preventsformation of the coating on the selected portions of the lamp burnerenvelopes. By way of example, with reference to FIG. 8, the resilientsleeve 99 provides a mask for the end portions 97 wherein the positionof the sleeve 99 is fixed relative to the end portions 97 during thecoating process.

Baking Processes:

Many coatings are formed by a reactive process, e.g., a silicon dioxide(SiO₂) coating may be formed by depositing silicon on the surface of thelamp burner envelope and reacting the silicon with oxygen to form thesilica. In order to obtain the desired physical characteristics such asthe optical qualities of the coating, it is often necessary to fullyreact the silicon deposited on the lamp burner envelope. Where thereaction process occurs during the deposition process, the rate ofdeposition of the silicon cannot exceed the reaction rate, i.e., eachlayer of the deposited silicon must be fully reacted before more siliconis deposited. The reaction between silicon and oxygen generally occursmore readily at higher temperatures, but the temperature of thedeposition process is generally between about 25° C. and 125° C. and islimited to about 200° C. or below.

One known method of reducing the time required to form a coating ofsilicon dioxide deposits the silicon at a rate in excess of the rate atwhich all of the deposited silicon will be reacted, and then bakes theincompletely reacted coatings in a reactive atmosphere at a temperatureabove 200° C. Thus the completion of the reaction may be bothaccelerated and take place in an oven, freeing the coating apparatus forreuse.

This known method is not particularly advantageous in the manufacturingof lamps wherein the step of sealing is performed before the step ofcoating because the temperature at which the coated lamp burners may bebaked must be limited to prevent undesirable oxidation of the electricalleads of the lamp burner. For example, the baking temperature of a lampburner having tungsten and molybdenum electrical leads must be limitedto less than about 400° C. in an atmosphere comprising essentially ofnormal dry air to prevent oxidation of the leads.

Where the coating step is performed before the sealing step, the coatedlamp burner envelopes do not include the electrical leads and thetemperature at which the coated lamp burner envelopes may be baked mayexceed 400° C., and may be as high as 1200° C., in normal dry air whichthereby reduces the time required for the bake.

However, it has been discovered that exposure of the coating totemperatures in excess of about 800° C. may deleteriously affect thephysical characteristics of the coating or cause mechanical failure ofthe coating upon cooling to room temperature. Some of the deleteriousaffects on the coating resulting from exposure of the coating to suchhigh temperatures and subsequent cooling of the coating are disclosed inU.S. Pat. No. 5,923,471 to Wood, II, et al. the contents of which isincorporated herein by reference. As suggested by the Wood, II, et al.patent, the baking process may be controlled depending on the specificmaterials comprising the coating to control the atomic structure of thecoating materials.

In the method of baking coated lamp burner envelopes of the presentinvention, the baking may be performed in steps, i.e., the bakingtemperature may be raised to a predetermined temperature for a period oftime and then the temperature may be further raised for a second periodof time, and the steps repeated as necessary until the final bakingtemperature is reached. The “recipe” for the baking process isdetermined by the specific materials comprising the coating in order tocontrol the atomic structure of the coating materials.

In still another aspect of the present invention, a method of bakingcoated lamp burners is provided wherein the coated lamp burners arebaked in an essentially reactive gas (e.g., oxygen) free atmosphere,e.g., an inert gas such as argon or nitrogen. Where the lamp burnerswith electrical leads are baked in an atmosphere which is essentiallyfree from oxygen, the temperature of the bake does not need to belimited to prevent oxidation of the electrical leads. Despite the lackof sufficient oxygen in the baking atmosphere to damage the electrodes,the reaction of the silicon may still be completed because of theunbonded oxygen dissolved in the coating.

Filament Positioning:

Where the coating is established before the sealing of the burner, thecoating may facilitate the positioning of the filament relative to thelamp burner envelope. In a halogen lamp having an IRR coating formed onthe surface of the lamp burner envelope, the heat reflected by the IRRcoating increases the temperature of the filament if properly focusedthereon and thus reduces the power necessary for proper lamp operation.Thus, the positioning of the filament relative to the lamp envelope isimportant. Optimally, the filament is positioned along the longitudinalaxis of the lamp burner envelope.

The temperature of the lamp filament will rise due to the passage ofelectrical current therethrough and the amount of light emitted by thefilament is proportional to the temperature of the filament. The degreeby which the temperature of the filament is raised by the reflectedinfrared radiation may be used as an indication of the position of thefilament relative to the lamp burner envelope.

FIG. 15 illustrates one embodiment of the present invention fordetermining the optimum position of the filament relative to the lampburner envelope in a halogen lamp. As shown in FIG. 15, the filament 152is positioned within the halogen lamp burner envelope 150 having an IRRcoating 154 formed on its exterior surface. The filament may be anymaterial suitable for providing light when an electrical current ispassed therethrough in a halogen lamp, typically tungsten. The filament152 is electrically connected to a source of power through the foils 158and the wires 160 passing through the unsealed burner envelope.

Because the IRR coating 154 has been previously formed on the lampburner envelope 150, the optimum position of the filament 152 relativeto the coated lamp burner envelope may be determined by measuring thepower required to maintain the temperature of the filament constantwhile adjusting the position of the filament. The temperature of thefilament in an operating halogen lamp is typically about 2900° C. Thetemperature of the filament during the alignment process may be muchlower. For example, the temperature of the filament may be maintained atabout 1500° C. during the alignment process.

The temperature of the filament may be measured by any conventionalmeans such as an optical pyrometer. Alternatively, the temperature ofthe filament may be determined by measuring the resistance of thefilament and determining the temperature using the knownresistance/temperature relationship for the filament. Preferably, theoptimum position of the filament relative to lamp burner envelope may bedetermined by:

-   -   a. positioning the filament relative to the burner envelope;    -   b. applying power to the filament;    -   b. measuring the temperature of the filament;    -   c. adjusting the power applied to the filament to attain a        predetermined filament temperature;    -   d. changing the position of the filament relative to the burner        envelope;    -   e. measuring the power applied to the filament;    -   f. adjusting the power applied to the filament to maintain the        temperature of the filament at the predetermined filament        temperature; and    -   g. determining the optimum position of the filament relative to        the burner envelope by repeating steps (b) to (f) as necessary        to determine the position of the filament relative to the burner        envelope wherein the minimum power is applied to the filament to        maintain the filament at the predetermined filament temperature.

Once the optimum position of the filament is determined through themovement of the filament relative to the burner envelope, the filamentmay be held in that position while the lamp burner envelope is sealed.

Protecting the Coating During the Seal:

FIG. 11 illustrates a conventional pinch sealing process for a glass orquartz glass lamp burner envelope where a selected portion 118 of theend portion 116 of the lamp burner envelope 114 is locally heated totemperatures between about 1700° C. and 2000° C. while collapsing theselected portion with the jaws 120 to form the hermetic seal.

FIG. 12 illustrates a conventional frit sealing process for a ceramiclamp burner envelope where a selected portion 122 of the end portion 124of the lamp burner envelope 126 may be locally heated to temperatures ofabout 1700° C. in order to melt the frit material 128 to thereby “plug”the end portion of the lamp burner envelope when the frit materialsolidifies upon cooling to form a hermetic seal.

The coating applied to the surface of the lamp burner envelope may havea deleterious effect on the pinch seal process. For example, a heatreflective coating may interfere with the localized heating of theselected portions to be pinched. Thus it may be desirable to mask theselected portions during the coating process.

In the sealing process, the temperature of the portions to be sealed israised to about 1700° C. or greater. The coating formed on the surfaceof the lamp burner envelope may be damaged if exposed to such hightemperatures. Thus it may be important to shield the coating from theflame during the sealing process.

As shown in FIG. 13, a suitable conventional heat reflecting shield 130may be provided between the heat sources 132 and the portions of thelamp burner envelope 134 having the coating 136 formed thereon.Alternatively as shown in FIG. 14, a suitable conventional heatreflective coating 138 such as alumina or zirconia may be formed on theportions of the lamp burner envelope 134 adjacent the selected portions140 of the lamp burner envelope 134 to be heated. The coating 138protects the area immediately adjacent the flame, and is not needed formore distant areas.

While preferred embodiments of the present invention have beendescribed, it is to be understood that the embodiments described areillustrative only and the scope of the invention is to be defined solelyby the appended claims when accorded a full range of equivalence, manyvariations and modifications naturally occurring to those of skill inthe art from a perusal hereof.

1-16. (canceled)
 17. In a process of depositing a layer of material onan array of elongated substrates in which the array is moved past one ormore sources of deposition material on a carrier while simultaneouslyrotating each substrate about its longitudinal axis, a method ofimproving the vertical density of the array comprising the steps ofsupporting one or more substrates on a single rod and rotating the rodto thereby rotate the substrates supported thereon about the axis formedby the rod.
 18. The method of claim 17 including the step of resilientlybinding adjacent of the substrates.
 19. The method of claim 17 whereinthe rod has a deformable surface in contact with each of the substratessupported thereon.
 20. The method of claim 17 wherein each of thesubstrates is internally supported on the rod.
 21. The method of claim17 wherein the carrier is a drum and the rod is vertical.
 22. The methodof claim 17 wherein the rod is frictionally engaged with the internalsurface of each substrate supported thereon to thereby prevent relativerotational movement between the rod and each substrate.
 23. The methodof claim 17 wherein the rod is horizontal.
 24. The method of claim 17 ina sputter deposition process.
 25. The method of claim 17 including thestep of masking the substrates so that the deposition material will notbe deposited on selected portions of the substrates.
 26. The method ofclaim 17 wherein the substrates are lamp burner envelopes.
 27. In aprocess of depositing a layer of material on an array of elongatedsubstrates in which the array is moved past one or more sources ofdeposition material on a carrier while simultaneously rotating eachsubstrate about its longitudinal axis, a method of improving thevertical density of the array comprising the steps of supporting one ormore substrates on a single vertical rod and rotating the lowest one ofthe substrates to thereby rotate all of substrates supported by the rodabout the axis formed by the rod.
 28. In a process of depositing a layerof material on an array of elongated substrates in which the array ismoved past one or more sources of deposition material on a carrier whilesimultaneously rotating each substrate about its longitudinal axis bysupporting each substrate on an axial rotation means, a method ofimproving the horizontal density of the array comprising the step ofalternating the vertical position of adjacent axial rotation means. 29.The method of claim 28 wherein the carrier is a cylindrical drumrotatable about its longitudinal axis wherein the longitudinal axis isvertical and one or more of the axial rotation means is a vertical rodwhich rotates each substrate supported thereon about the axis formed bythe rod. 30-39. (canceled)
 40. In a process for assembling a halogenlamp having an IRR coating on the lamp burner envelope, the step ofdetermining the optimum position of the filament relative to the burnerenvelope by measuring the electrical resistance of the filament.
 41. Ina process for aligning the filament in an IRR coated burner envelope inthe assembly of a lamp, the step of determining the optimum position ofthe filament relative to the burner envelope by measuring the powerapplied to the filament to maintain a constant temperature of thefilament.
 42. In a process for aligning the filament in an IRR coatedburner envelope in the assembly of a lamp, the step of determining theoptimum position of the filament relative to the burner envelope bymeasuring the temperature of the filament while maintaining the powerapplied to the filament at a constant.
 43. A method of aligning thefilament in an IRR coated burner envelope in the assembly of a lampcomprising the steps of: a. positioning the filament relative to theburner envelope; b. applying power to the filament; c. measuring thetemperature of the filament; d. adjusting the power applied to thefilament to attain a predetermined filament temperature; e. changing theposition of the filament relative to the burner envelope; f. measuringthe power applied to the filament; g. adjusting the power applied to thefilament to maintain the temperature of the filament at thepredetermined filament temperature; h. determining the optimum positionof the filament relative to the burner envelope by repeating steps (b)to (f) as necessary to determine the position of the filament relativeto the burner envelope wherein the minimum power is applied to thefilament to maintain the filament at the predetermined filamenttemperature.
 44. The method of claim 43 wherein the predeterminedfilament temperature is about 1500° C. 45-48. (canceled)
 49. A coatedlamp burner envelope comprising a generally tubular unsealed section oflight transmitting material having one or more materials deposited on atleast a portion of the exterior surface thereof to form a coating.
 50. Acoated lamp burner envelope comprising (i) a generally tubular sectionof light transmitting material suitable for forming the light emittingchamber of a lamp burner by sealing the end portions thereof, and (ii) afirst coating formed on at least a portion of the exterior surface ofsaid section, whereby the end portions of said section are not sealed.51. The coated lamp burner envelope of claim 50 further comprising asecond coating formed on one or more selected portions of the exteriorsurface of said section.
 52. A sealed lamp burner having a first coatingformed on at least a portion of the exterior surface thereof and asecond coating formed on the portions of the surface of said burneradjacent the end portions of the burner, said second coating beingsuitable for preventing the exposure of the first coating totemperatures greater than a certain temperature when selected portionsof the end portions of said burner are exposed to temperatures greaterthan the certain temperature.
 53. A section of light transmittingmaterial suitable for forming a lamp burner, said section having acoating formed on at least a portion of the exterior surface thereof,said coating comprising (i) one or more oxidized and unoxidizedmaterials and (ii) sufficient unbonded oxygen dissolved therein so thatthe unbonded oxygen will oxidize some or all of the unoxidized materialwhen exposed to high temperatures.
 54. A generally tubular section oflight transmitting material suitable for forming a plurality of lampburner envelopes by transversely cutting the section at selectedlocations along the length thereof, said section having a coating formedon at least a portion of the exterior surface of said section, wherebythe coating is formed before the section is cut.
 55. In an apparatus foruniformly depositing a layer of one or more materials on an array ofelongated substrates including a carrier for carrying the array past oneor more sources of the material to be deposited and a means for rotatingeach substrate about its longitudinal axis, the improvement wherein theaxial rotation means comprises one or more elongated rods each havingone or more substrates supported thereon for rotating the substratessupported thereon about the axis formed by the rod.
 56. The apparatus ofclaim 55 wherein the carrier comprises a cylindrical drum which isrotatable about its longitudinal axis, said drum carrying a plurality ofaxial rotation means spaced apart about the circumference of the drum.57. The apparatus of claim 55 wherein the rod is frictionally engagedwith the internal surface each substrate supported thereon.
 58. Theapparatus of claim 55 wherein the carrier comprises a flat surface whichis linearly transported past the sources of the material to bedeposited.
 59. In an apparatus for determining the optimum position ofthe filament relative to the lamp burner envelope of a halogen lamp,said apparatus including a means for positioning the filament relativeto the lamp burner envelope, the improvement wherein the apparatusfurther comprises a means for measuring the electrical resistance of thefilament.
 60. In an apparatus for determining the optimum position ofthe filament relative to the lamp burner envelope of a halogen lamp,said apparatus including a means for positioning the filament relativeto the lamp burner envelope, the improvement wherein the apparatusfurther comprises a means for measuring the temperature of the filament.61. An apparatus for aligning the filament relative to the lamp burnerenvelope in an IRR coated halogen lamp comprising: a. means forpositioning the filament relative to the burner envelope; b. a source ofelectrical power operably connected to the filament; c. a temperaturemeasuring device for measuring the temperature of the filament; and d.an electrical power measuring device for measuring the electrical powerapplied to the filament.